Today LED lighting technology is rapidly replacing traditional incandescent and fluorescent lights. Even in the tube lamp applications, instead of being filled with inert gas and mercury as found in fluorescent tube lamps, the LED tube lamps are mercury-free. Thus, it is no surprised that LED tube lamps are becoming highly desired illumination option among different available lighting systems used in homes and workplace, which used to be dominated by traditional lighting options such as compact fluorescent light bulbs (CFLs) and fluorescent tube lamps. Benefits of the LED tube lamps include improved durability and longevity, and far less energy consumption, therefore, when taking into of all factors, they would be considered as cost effective lighting option.
There are several types of LED tube lamps that are currently available on the market today. Many of the conventional LED tube lamp has a housing that use material such as an aluminum alloy combined with a plastic cover, or made of all-plastic tube construction. The lighting sources usually adopt multiple rows of assembled individual chip LEDs (single LED per chip) being welded on circuit boards, and the circuit boards are secured to the heat dissipating housing. Because this type of aluminum alloy housing is a conductive material, thus is prone to result in electrical shock accidents to users. In addition, the light transmittance of the plastic cover or the plastic tube diminish over time due to aging, thereby reducing the overall lighting or luminous efficiency of the conventional LED tube lamp. Furthermore, grainy visual appearance and other derived problems reduce the luminous efficiency, thereby reducing the overall effectiveness of the use of LED tube lamp. The LED light sources are typically a plurality of spatially arranged LED chips. With respect to each LED chip, due to its intrinsic illumination property, if there was no any sufficient further optical processing, the entire tube light will exhibit grainy or non-uniform illumination effect; as a result, grainy effect is produced to the viewer or user, thereby negatively affect visual aesthetics thereof. In other words, the overall illumination distribution uniformity of the light outputted by the LED light sources without having additional optical processing techniques or structures for modifying the illumination path and uniformity would not be sufficient enough to satisfy the quality and aesthetics requirements of average consumers.
Referring to US patent publication no. 2014226320, as an illustrative example of a conventional LED tube lamp, the two ends of the tube are not curved down to allow the end caps at the connecting region with the body of the lamp tube (including a lens, which typically is made of glass or clear plastic) requiring to have a transition region. During shipping or transport of the LED tube lamp, the shipping packaging support/bracket only makes direct contact with the end caps, thus rendering the end caps as being the only load/stress points, which can easily lead to breakage at the transition region with the glass lens.
With regards to the conventional technology directing to glass tube of the LED tube lamps, LED chip on board is mounted inside the glass-tubed tube lamp by means of adhesive. The end caps are made of a plastic material, and are also secured to the glass tube using adhesive, and at the same time the end cap is electrically connected to the power supply inside tube lamp and the LED chip on boards. This type of LED tube lamp assembly technique resolves the issue relating to electrical shocks caused by the housing and poor luminous transmittance issues. But this type of conventional tube lamp configured with the plastic end caps requires a tedious process for performing adhesive bonding attachment because the adhesive bonding process requires a significant amount of time to perform, leading to production bottleneck or difficulties. In addition, manual operation or labor are required to perform such adhesive bonding process, thus would be difficult for manufacturing optimization using automation. In addition, sometimes the end cap and the glass lamp tube may come apart from one another when the adhesive does not sufficiently bond the two, thus the detachment of the end cap and the glass lamp tube can be a problem yet to be solved.
In addition, the glass tube is a fragile breakable part, thus when the glass tube is partially broken in certain portion thereof, would possibly contact the internal LED chip on boards when illuminated, causing electrical shock incidents. Referring to Chinese patent publication no. 102518972, which discloses the connection structure of the lamp caps and the glass tube, as shown in FIG. 1 of the aforementioned Chinese patent reference, it can be seen that the lamp end cap protrudes outward at the joining location with the glass tube, which is commonly done in the conventional market place. According to conducted studies, during the shipping process of the LED tube lamps, the shipping packaging support/bracket only makes contact with the lamp end caps, which make the end caps as being the only load/stress points, which can easily lead to breakage at the transition coupling regions at the ends of the glass tube. In addition, with regards to the secure mounting method of the lamp end caps and the glass tube, regardless of whether using hot melt adhesive or silicone adhesive, it is hard to prevent the buildup and light blockage of excess (overflown) leftover adhesive residues, as well as having unpleasant aesthetic appearance thereof. In addition, large amount of manpower is required for cleaning off of the excessive adhesive buildup, creating further production bottleneck and inefficiency. As shown also from FIGS. 3 and 4 of the aforementioned Chinese patent application, the LED lighting elements and the power supply module require to be electrically connected via wire bonding technique, and can be a problem or issue during shipping due to the concern of breakage.
Based on the above, it can be appreciated that the LED tube lamp fabricated according to the conventional assembly and fabrication methods in mass production and shipping process can experience various quality issues and are in need of improvements to be made. Referring to US patent publication no. 20100103673, which discloses of an end cap substitute for sealing and inserting into the housing. However, based on various experimentation, upon exerting a force on the glass housing, breakages can easily occur, which lead to product defect and quality issues. Meanwhile, grainy visual appearances are also often found in the aforementioned conventional LED tube lamp.